As a power source for a hybrid vehicle and an electric vehicle such as a plug-in electric vehicle which have been widely accepted in recent years, a rectangular rechargeable nonaqueous electrolyte secondary battery, for example, a lithium ion secondary battery have been mainly used. The lithium ion secondary battery comprises an electrode group in which a positive electrode and a negative electrode are wound or stacked with a separator interposed, a battery container (battery case) accommodating the electrode group, and a nonaqueous electrolyte solution in which the electrode group accommodated in the battery container is immersed. The battery container is available from, for example, aluminum or aluminum alloy and is rectangular in shape.
A power source for an electric vehicle needs a nonaqueous electrolyte secondary battery strong enough to withstand shock and vibration. For this purpose, a vibration absorbing member is used.
A lithium ion secondary battery is configured such that, for example, members using an insulation resin are disposed around leads for connecting a positive terminal (positive electrode) and a negative terminal (negative electrode) fixed on a cover of a battery container with a positive electrode and a negative electrode of an electrode group, providing the functions of vibration absorption and insulation from the battery container. However, if a brittle material or a low strength material is used as the vibration absorbing member, shock and vibration cause breaking of the lead. Therefore, a material with an appropriately low elastic modulus has to be used. However, since materials with the low elastic modulus are often high in specific heat, there is a problem that frictional heat generated by vibration is likely to accumulate, reducing the material strength by heat generated, resulting in poor resistance to shock and vibration.